题解 | #矩阵乘法计算量估算#
矩阵乘法计算量估算
https://www.nowcoder.com/practice/15e41630514445719a942e004edc0a5b
n = int(input())
ls = []
for i in range(n):
ls.append(list(map(int,input().split())))
s = input() # (A(BC))
stack = []
cc = 0
for i in s:
if i.isalpha():
stack.append(ls[ord(i)-65])
elif i == ')' and len(stack) >= 2:
a = stack.pop()
b = stack.pop()
cc += a[0]*a[1]*b[0]
stack.append([b[0],a[1]])
print(cc)